It’s mid-October, so it’s the right time for a midseason progress report on the Oklahoma defense. It’s been an interesting ride for the Sooners, who have looked outstanding against Texas Tech and Texas but struggled to get key stops in OU’s lone loss to Kansas State.

Nonetheless it’s obvious how much OU’s defense has improved during Mike Stoops' return as defensive coordinator. The Sooners rank No. 14 nationally in total defense and No. 20 nationally in scoring defense. Here’s what we’ve learned about OU’s defense after five games:

After moving to free safety before the season, Tony Jefferson has excelled in coverage and helping to stop the run.

Defensive MVP:Tony Jefferson. The junior has brought consistency and playmaking to the free safety spot this season. He leads OU with 37 tackles, including 25 solo. And, more importantly, he’s shown a measure of toughness while playing at less than 100 percent with a ankle injury suffered against Florida A&M. He’s been productive and has led by example.

Most surprising player:Javon Harris. The senior took a ton of abuse after his subpar end to the 2011 season. Yet Harris shook off the critics’ harsh words and has performed at a high level in 2012. He’s second on the team with 30 tackles, including one tackle for loss and two interceptions.

Defining moment of the first five games:Aaron Colvin’s interception against Texas Tech. Colvin’s play against the Red Raiders was a prime example of how well he’s played this season. It was a play very few players could make. And he’s played that way all season.

Most concerning moment of the first five games:Travis Harvey's 75-yard touchdown for Florida A&M. It was a troubling moment for Sooners fans because it was the result of a blown coverage in the secondary. Cornerback Demontre Hurst was beaten at the line of scrimmage and safety Jesse Paulsen wasn’t in position to make a play on the ball, resulting in a long touchdown for the Rattlers.

Player to watch the rest of the season:Frank Shannon. The redshirt freshman linebacker has showed signs of becoming a big-time playmaker in OU’s defense. His six tackles and one sack against Texas Tech was one of the best performances of the year by a Sooners linebacker. It could just be a matter of time before Shannon emerges as a core contributor.

Unsung hero:David King. It’s hard to imagine where the Sooners would be without King. He stepped in at defensive tackle for Casey Walker when he was forced to miss OU’s first two games. He’s played defensive end and defensive tackle at various times this season and has held his own for the Sooners. His leadership has also been a key as he helped OU overcome its loss to Kansas State and rebound for back-to-back wins over Texas Tech and Texas.